1. Field of the Invention
The present invention relates to a method of and an apparatus for generating image data of a reduced image based on multi-color image data consisting of pixel codes, which represent an original image including characters or plane figures.
2. Description of the Prior Art
Since image processing workstations generally deal with image data with a relatively high resolution, such image data is reduced by lowering the resolution before it is output to a printer or a display of a relatively lower resolution. Here the reduction denotes decrease in the number of pixels constituting one image, i.e., a reduced resolution, and does not always mean contraction of an actual image size.
A reduced resolution image generator for generating a reduced image, for example, successively extracts image data of one pixel at a predetermined position from every 2.times.2 pixel unit in a whole image and forms a reduced image with the extracted image data. The reduction factor is four in this case.
FIG. 1A shows an example of such a prior art reduction process. The image of FIG. 1A includes lines consisting of pixels with a predetermined color code, which are filled with slant lines. Pixel data at the left upper position within each 2.times.2 pixel unit is extracted. The left upper position is given an open circle in FIG. 1A. For example, pixel data D(1,1) is extracted from the unit including pixel data D(1,1), D(2,1), D(1,2), and D(2,2). Pixel data D(3,1) is extracted from another unit including pixel data D(3,1), D(4,1), D(3,2), and D(4,2). The extraction process is repeated for the whole image, and a reduced image shown in FIG. 1B is generated based on the extracted pixel data.
Since the conventional reduced image generator extracts a pixel data at a predetermined position in each pixel unit, a line one pixel wide sometimes disappears from a resultant reduced image. For example, part of the lines in the original image of FIG. 1A disappears in the reduced image shown in FIG. 1B.
In a linework image including characters or figures, such line missing causes distortion of the characters or plane figures.